Conventionally, a cylindrical roller bearing and a deep groove ball bearing are used as a bearing used in a main motor for a railway vehicle. For example, a cylindrical roller bearing 1 shown in FIG. 17 comprises an inner ring 2, an outer ring 3, cylindrical rollers 4 as rolling bodies arranged between the inner ring 2 and the outer ring 3, and a retainer 5 retaining intervals of the cylindrical rollers 4.
In addition, according to the cylindrical roller bearing 1 used in the main motor for the railway vehicle, an insulation layer 3a is formed on an outer diameter surface and both end faces of the outer ring 3 in order to prevent damage of the bearing due to electric corrosion. The insulation layer 3a is formed by spraying an insulation material such as ceramics.
In addition, since the main motor for the railway vehicle is used outdoors, in a case of an open-type bearing having a grease pocket in a bearing peripheral structure, grease could deteriorate due to entering of dust. Thus, a cylindrical roller bearing 41 shown in FIG. 1 is a sealed-type bearing in order to prevent grease from deteriorating due to entering of dust and in order to lengthen a maintenance cycle.
Meanwhile, according to the conventional cylindrical roller bearing 1 shown in FIG. 17, when a relation between a length L1 of the roller 4 and an axial width W1 of the inner ring 2 and the outer ring 3 satisfies L1/W1≧0.4, that is, a ratio of the roller length L1 to the axial width W1 is high, a bearing volume V1 and an internal space capacity C1 are designed so that a relation between them satisfies C1/V1≈0.2, and a diameter A1 of the roller 4 and a bearing thickness dimension T1 are designed so that a relation between them satisfies 0.25≦A1/T1≦0.55 in general.
In addition, the “bearing volume” in this specification designates a volume surrounded by an inner diameter surface of the inner ring and an outer diameter surface of the outer ring and end faces of the inner and outer rings of the bearing, and according to the example shown in FIG. 17, it is calculated by the following formula using an outer diameter dimension D1 of the outer ring 3, an inner diameter dimension d1 of the inner ring 2, the axial width W1, and pi π.
                              V          1                =                              π            ×                          (                                                                    (                                                                  D                        1                                            2                                        )                                    2                                -                                                      (                                                                  d                        1                                            2                                        )                                    2                                            )                        ×                          W              1                                1000                                    [                  Formula          ⁢                                          ⁢          1                ]            
In addition, the “internal space capacity” in this specification designates a space surrounded by the inner ring, the outer ring, and the sealing seal.
According to the cylindrical roller bearing provided within the above range, since the bearing internal space capacity C1 is small, the problem is that an appropriate amount of grease to ensure a bearing life required in the bearing for the railway vehicle main motor cannot be enclosed. In addition, the same is true in a ball bearing shown in FIG. 18.
The ball bearing shown in FIG. 18 comprises an inner ring 12, an outer ring 13 having an insulation layer 13a, balls 14 arranged between the inner ring 12 and the outer ring 13, and a retainer 15 retaining intervals of the balls 14. Thus, when a relation between a diameter A2 of the ball 14 and an axial width W2 of the inner ring 12 and the outer ring 13 satisfies A2/W2≧0.4, a bearing volume V2 and an internal space capacity C2 are designed so that a relation between them satisfies C2/V2≈0.3, and the diameter A2 of the ball 14 and a bearing thickness dimension T2 are designed so that a relation between them satisfies 0.4≦A2/T2≦0.6 in general.
To increase a supplying ratio of the grease to the internal space capacity can be a way of solving the above problem, but in this case, since stirring resistance of the grease is increased while the bearing is rotated, and especially at the time of starting, so that the temperature of the bearing could be abruptly increased, which is not appropriate.
Thus, a sealed-type cylindrical roller bearing in which an appropriate amount of grease can be ensured is disclosed in Japanese Unexamined Patent Publication No. 2003-13971 and Japanese Unexamined Patent Publication No. 2004-346972, for example.
As shown in FIG. 19, a cylindrical roller bearing 21 described in the Japanese Unexamined Patent Publication No. 2003-13971 comprises an inner ring 22 having a long axial width, an outer ring 23, cylindrical rollers 24 arranged between the inner ring 22 and the outer ring 23, a retainer 25 retaining intervals of the cylindrical rollers 24, and a sealing seal 26 of an L shape in cross section to enclose grease in the bearing. The sealing seal 26 is manufactured by covering a cored bar 26a with an insulation resin 26b. In addition, an insulation layer is formed on an outer diameter surface and both end faces of the outer ring 23.
In addition, as shown in FIG. 20, a cylindrical roller bearing 31 described in the Japanese Unexamined Patent Publication No. 2004-346972 comprises an inner ring 32, an outer ring 33, cylindrical rollers 34 arranged between the inner ring 32 and the outer ring 33, a retainer 35 retaining intervals of the cylindrical rollers 34, and a sealing seal 36 having a channel-shaped configuration projecting from both end faces of the inner ring 32 and the outer ring 33, and an outer diameter surface and both end faces of the outer ring 33 is covered with an insulation material 33a. In addition, the sealing seal 36 is in the form of the channel shape projecting from both end faces of the inner ring 32 and the outer ring 33, and fixed to the outer ring 33 by a stopper 36a. According to the cylindrical roller bearing 31 described in the above document, since the sealing seal 36 projecting from the end face of the bearing functions as a grease pocket, an amount of grease that can be enclosed in the bearing is increased.
However, when the projecting amount of the sealing seal 26, 36 is small, an appropriate amount of grease cannot be enclosed as a result, and when the projecting amount of the sealing seal 26, 36 is large, as grease existing at a position far from the center of the bearing does not contribute to the lubrication of the bearing at all. However, there is no description of the appropriate projecting amount of the sealing seal 26, 36 in the above document.
Furthermore, according to the cylindrical roller bearing 21 shown in FIG. 19, since the inner ring 22 has a specific configuration, a standard product cannot be used for it. As a result, manufacturing cost of the cylindrical roller bearing 21 is increased.
In addition, the cylindrical roller bearing 31 having the above constitution has the problem that when the viscosity of the grease is lowered due to an increase in temperature at the time of rotation of the bearing, the grease in the grease pocket is concentrated at the lower part of the bearing. When such grease flows into the bearing in large amounts, stirring resistance is increased and a temperature could rise abruptly.
Thus, according to the cylindrical roller bearing 31 shown in FIG. 20, the grease pocket is divided into a plurality of regions by weirs 37 projecting from an inner wall surface of the sealing seal 36 so that the grease can be uniformly distributed in the grease pocket. Thus, the grease is prevented 1=from congregating on the lower side of the bearing.
However, according to the sealing seal 36 used in the cylindrical roller bearing 31 shown in FIG. 20, the plurality of weirs 37 are arranged at the same intervals. When such cylindrical roller bearing 31 supports the rotation shaft extending in the horizontal direction, the weirs 37 arranged on the right and left sides of the rotation shaft can prevent the grease from flowing from the upper part to the lower part of the bearing effectively. However, the weirs provided on upper and lower sides of the rotation shaft do not contribute to retaining of grease so much.
In addition, although the sealing seal 36 used in the cylindrical roller bearing 31 shown in FIG. 20 can prevent the grease in the grease pocket from concentrating at the lower part of the bearing, it cannot prevent the grease in the grease pocket from flowing into the bearing excessively. When the grease more than necessary flows into the bearing, the stirring resistance is increased and the temperature of the bearing rises.
Furthermore, according to the cylindrical roller bearing 31 shown in FIG. 20, at the time of rotating, the outer ring 33 and the sealing seal 36 do not move and the inner ring 32 rotates with the rotation of the shaft. Thus, in order to prevent the sealing seal 36 from being damaged by the contact between the inner ring 32 and the sealing seal 36, it is necessary to provide a gap between the inner ring 32 and the sealing seal 36 to some extent.
When this gap is too small, the inner ring 32 could come into contact with the sealing seal 36 during the rotation of the bearing due to a manufacturing error of the sealing seal 36 and the like. Meanwhile, when it is too large, the grease cannot be prevented from leaking and dust could enter from the outside.
In addition, the seal having the grease pocket is mounted on the rolling bearing after the grease has been enclosed. The grease is enclosed in the grease pocket of the seal by a spot enclosing method using a grease enclosing device having a grease inlet and a grease outlet in general.
Here, one example of the enclosing method of the grease will be briefly described. First, a structure of the grease enclosing device will be described. FIG. 21 is a sectional view showing a part of the grease enclosing device, and FIG. 22 is a view of the grease enclosing device shown in FIG. 21 seen from a direction of an arrow Z of FIG. 21. Referring to FIGS. 21 and 22, the grease enclosing device 21 comprises a grease inlet 122 through which the grease is supplied from the outside 125 to the grease enclosing device 121, a guiding part 123 guiding the grease from the grease inlet 122 to a grease outlet 124, a plurality of grease outlets 124 through which the grease is discharged into a grease pocket 126, and a seal mounting surface 130 positioned at a lower part of the grease enclosing device 121 and comprising the plurality of grease outlets 124.
Next, the grease enclosing method will be described with reference to FIGS. 21 and 22. First, a seal 131 having the grease pocket 126 is mounted on the lower part of the seal mounting surface 130. Next, grease 127 is supplied from the outside 125 to the grease inlet 122. Thus, the grease 127 supplied into the grease enclosing device 121 flows in the directions shown by arrows X and Y shown in FIG. 21 through the guiding part 123 and reaches the plurality of grease outlets 124. Then, the grease 127 is discharged from the plurality of grease outlets 124 and supplied to the grease pocket 126 of the seal 131. Thus, the grease 127 is enclosed in the grease pocket 126.
When the grease 127 is enclosed in the grease pocket, in the case where the consistency of the grease 127 is not appropriate, the grease 127 could not been appropriately enclosed in the grease pocket 126.
This will be described in detail with reference to FIG. 23. FIG. 23 is a view showing a state in which the grease 127 having a low consistency is enclosed in the grease pocket 126 of the seal 131. Referring to FIG. 23, in the case where the consistency of the sealed grease 127 to be enclosed is low, that is, the grease 127 is in a hard state, when the grease 127 is enclosed in the grease pocket 126 of the seal 131, it is accumulated in the vicinity of a just lower part of the grease outlet 124 in a solid state. In this case, a space 129 is generated in the grease pocket 126 of the seal 131, specifically, on the side of an inner wall surface 128 of the grease pocket 126. In this case, even after the grease 127 has been discharged from the grease outlet 124 and the enclosing of the grease 127 has been completed, the space 129 still exists.
Since the grease 127 is not provided at the space 129, that space 129 is wasted in the grease pocket 126. The amount of the grease 127 enclosed in this state is not enough for maintaining a lubricating property for a long time.
In addition, the grease 127 is not in contact with the inner wall surface 128 of the grease pocket 126 at this space 129. The grease 127 that is not in contact with the inner wall surface 128 of the grease pocket 126 is low in retention force, so that it drops out of the grease pocket 126 easily. When it drops out, a large amount of the grease 127 flows in the bearing at one time, and this could cause abnormal heat generation due to an increase in stirring resistance.
Meanwhile, in the case where the consistency of the grease 127 to be enclosed is high, that is, the grease 127 is in a soft state, when the grease 127 is enclosed, the above problem does not arise and the grease 127 is supplied to the inner wall surface 128 of the grease pocket 126 and enclosed without any space.
However, since the consistency of the sealed grease 127 is high, its fluidity is high and retention force in the grease pocket 126 is low, so that the grease 127 easily drops out of the grease pocket 126. Especially, when the grease 127 is enclosed in the grease pocket 126 having large capacity, the degree of freedom of the movement is high, so that the retention force of the grease 127 in the grease pocket 126 have to be high. However, when the consistency of the grease 127 is high, the retention force is not enough and a large amount of grease 127 flows in the rolling bearing at one time and as a result, abnormal heat could be generated due to an increase in stirring resistance.
When the rolling bearing having the above problem is used in the spindle support structure supporting the spindle of the main motor for the railway vehicle, it could not be used for a long period of time.